The objectives of this project are (1) to monitor cell mediated and humoral immune responses to Chlamydia trachomatia (Ct) in women with chlamydial infection of the genital tract during pregnacy, (2) to study the development of humoral and cell mediated immunity (CMI) to Ct in infants who are exposed to this organism at birth, and (3) to correlate immunologic responsiveness of infants with occurrence of chlamydial disease. Infection in pregnant women will be detected by chlamydial cultures of endocervical swabs obtained at 8-12 and 36-38 weeks of gestation. Antibody and CMI studies will also be performed at these times. Infection in infants will be detected by culture of conjunctival, rectal, and vaginal swabs and nasopharyngeal aspirates collected at 2 and 6 weeks and 3 and 6 months of age. Antibody titers in blood collected at 6 months of age will be compared with cord blood antibody titers to detect seroconversion. Development of chlamydial CMI will be monitored by tests of lymphocyte responsiveness to Ct antigen performed on blood specimens obtained from infants at 2 and 6 weeks and 3 and 6 months of age, and on placental blood. Speciments will be tested for Ct by inoculation into cycloheximide-treated McCoy cell coverslip cultures. Chyamydial CMI will be measured by the blastogenic response (tritiated thymidine uptake) of lymphocyte cultures exposed in vitro to Ct antigen in comparison to the response of lymphocyte cultures exposed to control material. Chlamydial antigen will consist of ultraviolet-activated purified elementary bodies of Ct, serotype E, prepared in cycloheximide-treated McCoy cell cultures. Control material will consist of fluids from uninfected McCoy cell cultures prepared in the same way as chlamydial antigen. Titers of circulating Ct antibodies will be measured by a single antigen (serotype LGV-2) immunofluorescence technique. The presence of CMI and humoral antibody in infected mothers and the development of these immunologic responses in infants will be correlated with the occurrence of chlamydial disease such as conjunctivitis and interstitial pneumonia during the first six months of life. These studies are expected to contribute to an understanding of the role of CMS and humoral antibody in resistance to and recovery from chlamydial infections.